Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$123.54	5.661%	$130.5336	$130.53	$130.55	$130.50
Purchase #2	$136.35	5.124%	$143.3366	$143.34	$143.35	$143.30
Purchase #3	$94.39	4.667%	$98.7952	$98.80	$98.80	$98.80
Purchase #4	$116.65	13.460%	$132.3511	$132.35	$132.35	$132.40
Purchase #5	$69.83	3.692%	$72.4081	$72.41	$72.40	$72.40
Purchase #6	$220.89	5.254%	$232.4956	$232.50	$232.50	$232.50
Purchase #7	$43.26	5.628%	$45.6947	$45.69	$45.70	$45.70
7 purchase totals =	$804.91		$855.6149	$855.62	$855.65	$855.60